The plan would boost the share of electricity Iowa generates from wind to 40% from 31%

Iowa, which already gets more of its power from wind than any other U.S. state, will become more reliant on the electricity source under a $3.6 billion plan announced Thursday by a utility owned by Warren Buffett’s Berkshire Hathaway Inc.

MidAmerican Energy Co. said Thursday that it is planning to build up to 2,000 additional megawatts of wind turbines with a goal of generating 85% of its power from wind. The company, based in Des...